JPH05249687A - Pattern forming method - Google Patents

Abstract

(57) [Abstract] [Purpose] A thin film on a high step substrate is etched with high precision by physical etching such as ion milling. [Structure] A thin film to be processed is patterned by using a photosensitive plasma-polymerized polysilane alone or a laminated film of this and a carbon film. [Effect] Plasma-polymerized polysilane has high sensitivity and
Since the step coverage is excellent, the thickness of the resist can be thinned in the step recesses, so it is possible to improve the resist pattern accuracy and prevent redeposition during ion milling, and to improve the pattern dimensional accuracy of the thin film to be processed. Has the effect of improving.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fine processing method in lithography technology, and more particularly, to a method for accurately processing a thin film on a substrate having a large step by a physical sputtering method.
And a thin film magnetic head formed by using this method.

[0002]

2. Description of the Related Art A method of forming a resist pattern on a thin film to be processed and removing the material to be processed in the resist-free portion of the resist pattern by ion milling to obtain a desired pattern is well known, and wet etching and reaction are performed. This is an essential method for microfabrication of difficult-to-process materials that cannot be processed by wet dry etching. As this resist, for example,
Phenol novolac-based resist (trade name: OFPR-800 manufactured by Tokyo Ohka) is used. In order to form a thin film, these resists are formed by a so-called spin coating method in which a resist material is dissolved in a solvent, dropped onto a thin film to be processed with an appropriate viscosity, and the substrate is rotated.

However, as devices and wirings have become multi-layered due to the high integration of integrated circuits and as the field of application of thin film technology has become wider, the necessity of patterning a thin film on a substrate having a large difference in height of irregularities has increased. .

However, when the resist is formed by the above-mentioned spin coating method, since the thickness of the resist is different between the concave portion and the convex portion on the substrate, there is a problem that the dimensional accuracy of the thick portion of the resist is significantly deteriorated.

In order to solve this problem, a pattern forming method using a laminated film in which an organic resin layer for flattening unevenness on the substrate is formed as a lower layer of a resist has been proposed. In particular, since the thickness of the flattening layer is thick and the wall surface is nearly vertical, when a method mainly involving physical sputtering is used, there is a re-adhesion phenomenon in which sputtered particles adhere to this wall surface. Occurs. This redeposition phenomenon deteriorates the dimensional accuracy and causes angular accumulation from the wall surface, resulting in undesired protrusions.

In order to solve this problem, Japanese Patent Laid-Open No. 63-
Japanese Patent No. 297435 proposes a pattern forming method using a two-layer film of a carbon film and a resist thin film formed by plasma polymerization.

[0007]

SUMMARY OF THE INVENTION The above-mentioned prior art is that a carbon film and a resist film are formed to have uniform thicknesses by forming a step, a layer for exposing and patterning, and a mask layer for resisting physical sputtering. Since it is composed of another material, the film thickness can be made thin, which is a very excellent method for highly accurate pattern formation.

However, since the resist formed by plasma polymerization is formed into a plasma state by using high frequency or the like for a monomer having a photosensitive group, it is inevitable that the photosensitive group is partially decomposed by high energy of plasma. .. Therefore, there is a problem that the generated resist has extremely low sensitivity.

An object of the present invention is to provide a method for forming a highly accurate pattern using a highly sensitive plasma-polymerized resist.

Another object of the present invention is to provide a thin film magnetic head in which a magnetic material for regulating a track width is patterned by using the method for forming a high precision pattern, and a manufacturing method thereof.

[0011]

The above object is to form a resist pattern on a substrate having a large height difference in the surface to be processed, and subject the material to be processed in a resist-free portion by a dry etching method mainly including physical sputtering. In the method of forming a pattern by removing the above, the resist is polysilane composed of repeating units represented by Chemical formula 5 or Chemical formula 6 formed by plasma polymerization, and the resist has a uniform film thickness in the surface to be processed. It is achieved by

[0012]

[Chemical 5] However, R ₁ and R ₂ represent different groups selected from a fluoro group, a perfluoroalkyl group, a phenyl group, a perfluorophenyl group, and a perfluoroalkyl-substituted phenyl group.

[0013]

[Chemical 6] However, R ₃ represents a perfluoroalkyl group or a perfluoroalkyl-substituted phenyl group.

The physical sputtering method referred to here is a method such as ion beam etching, ion milling, sputter etching or the like, in which the material to be processed is repelled mainly by the impact of ions.

Further, the above object is to provide a second layer which is difficult to be removed by the oxygen plasma and which can be patterned by electromagnetic wave or particle beam irradiation and a phenomenon on the first layer which can be removed by the oxygen plasma. In a method of patterning a material to be processed of a substrate having a large height difference in a surface to be processed by using a formed laminated film having a two-layer structure, the second layer formed by plasma polymerization is used. This is achieved by using a polysilane composed of the repeating unit represented by Chemical formula 6.

Furthermore, the above object can be achieved by patterning a magnetic material which regulates the track width of a thin film magnetic head using the pattern forming method.

The polysilane formed by plasma polymerization of the present invention is a compound represented by Chemical formula 1 and Chemical formula 2. Two substituents of dihydrosilane, R ₁ and R ₂ are fluoro groups,
When they are different groups selected from a perfluoroalkyl group, a phenyl group, a perfluorophenyl group, and a perfluoroalkyl-substituted phenyl group, they are polysilanes represented by Chemical formula 1 and dihydrosilanes of 2 When the two substituents are the same R ₃ and are a perfluoroalkyl group or a perfluoroalkyl-substituted phenyl group, it is a polysilane represented by Chemical formula 2 and its molecular structure is one-dimensional such as tetrahydrofuran. It is soluble in organic solvents. Here, examples of the perfluoroalkyl group include a perfluoromethyl group, a perfluoroethyl group, a perfluoropropyl group, a perfluorobutyl group, a perfluorohexyl group, and the like. Examples of the substituted phenyl group include a phenyl group substituted with the above perfluoroalkyl group.

Regarding the plasma polymerization method used in the synthesis of the one-dimensional soluble polysilane of the present invention, Techniques and App
lications of Plasma Chemistry edited by JR Holl
It can be performed under general conditions as described in ahanand AT Bell, John Wiley & Sons 1974. That is, a vacuum chamber equipped with two electrodes (usually parallel plates) is evacuated and a monomer gas is introduced into the chamber. Then, a high frequency is applied between the electrodes to cause a discharge, and a plasma of a monomer gas is generated. The polymer is deposited on the substrate placed on the ground electrode. In order to suppress cross-linking as much as possible, it is usually better to choose weak plasma conditions. For example, it is preferable that the applied power is small, the substrate temperature is low, the monomer gas flow rate is small, and the monomer gas pressure is set high.

The polysilane formed on the substrate is crack-free up to a thickness of about 3 μm and has no pinholes up to a thickness of about 0.01 μm. When this substrate was put into tetrahydrofuran, polysilane was dissolved, and the molecular weight was measured by gel permeation chromatography, and it was about 1,000 to 500,000 in terms of polystyrene.

[0020]

In the plasma polymerization method, a thin film of an organic compound can be formed to have almost the same film thickness even at a high step portion, a low step portion, or a sloped portion on the substrate. By having
It is possible to process a thin film to be processed having a step into a highly accurate pattern in any part. Here, the photosensitivity is ultraviolet light,
It has the property of being sensitive to deep ultraviolet rays, electron beams, and X-rays.

However, when an attempt is made to form a photoresist by plasma polymerization, the polymer usually has a three-dimensionally crosslinked structure. This is because the energy of plasma is much larger than the bond dissociation energy of organic substances. The three-dimensional cross-linked polymer has no photosensitivity, or even if it exists, its sensitivity is extremely low and not practical.

Therefore, in order to improve the sensitivity of the photoresist formed by plasma polymerization, it is necessary to devise the conditions of plasma polymerization. For example, Japanese Patent Publication No. 2-575
The method of reducing the energy of plasma and reducing the three-dimensional cross-linking structure as disclosed in Japanese Patent Laid-Open No. 62-62 is effective. However, this is still insufficient to satisfy high-performance properties such as the sensitivity of photoresist. This is because the monomer molecule has a low reaction selectivity.

Therefore, the inventors considered that the selectivity of the reaction is provided by making a difference in bond dissociation energy in the molecule. First, ab-
Initio calculation was performed to determine the bond dissociation energy.

[0024]

[Chemical 7]

[0025]

[Chemical 8] However, Ph represents a phenyl group.

[0026]

[Chemical 9] However, Ph represents a phenyl group.

The Si-H bond dissociation energy of monosilane represented by Chemical formula 7 was calculated to be 84.3 kcal / mol. Chemical formula 7 has four Si-H bonds equivalent to each other, and three-dimensional crosslinking is unavoidable even if the polymerization is carried out under weak plasma conditions, and the structure is one-dimensionally (linear). You can't control it.

On the other hand, S of phenylsilane represented by Chemical formula 8
i-H bond dissociation energy is 85.5 kcal / mol,
Si-Ph bond dissociation energy is 124.7 kcal /
calculated as mol. The difference in bond dissociation energy between Si-H and Si-Ph is 39.2 kcal / mol, and it is sufficiently possible to control the plasma polymerization reaction and regulate only the dissociation of Si-H. However, the equivalent Si-H bond is 3
Therefore, the possibility of three-dimensional crosslinking still remains, and the structure of the polymer cannot be highly regulated in one dimension.

On the other hand, the Si—H bond dissociation energy of the model compound phenylfluorosilane represented by Chemical formula 9 is 1
It was calculated that 07.6 kcal / mol, Si-Ph bond dissociation energy was 131.6 kcal / mol, and Si-F bond dissociation energy was 153.7 kcal / mol.
By changing one of the three Si-H bonds of phenylsilane to a Si-F bond having a large bond dissociation energy, the bond having the smallest bond dissociation energy is converted into two S bonds.
It could be an i-H bond. However, due to the introduction of F atom, Si- having the next smallest bond dissociation energy-
The difference between the bond dissociation energy and the Ph bond is 24.0 kca.
It became as small as 1 / mol. However, this energy difference can control the plasma polymerization reaction and regulate only the Si—H dissociation reaction. Moreover, since there are only two Si—H bonds having the smallest bond dissociation energy, the structure of the polymer can be highly regulated one-dimensionally.

When the plasma-polymerized polysilane formed from such a model compound is irradiated with ultraviolet rays, it is exposed to Si--Si.
The bond is cleaved, and a difference in molecular weight between exposed and unexposed areas is created. When this is developed with an organic solvent, the exposed area is dissolved to give a positive pattern.

The above-mentioned plasma-polymerized polysilane having photosensitivity is difficult to be etched by oxygen plasma, and in the case where it has a structure in which a thin film which is easily etched by oxygen plasma and is hard to be physically sputtered is formed under the film, the photosensitive layer is formed. By sequentially transferring the pattern printed on the lower layer to the lower layer, the thin film to be processed made of a difficult-to-process material can be processed with high accuracy.

[0032]

Embodiments of the present invention will be described below with reference to FIGS. These drawings are process diagrams showing one embodiment of the pattern forming method of the present invention. FIG. 1 shows a pattern type method using only a plasma-polymerized film, and FIG. 2 shows pattern formation using a laminated film having a two-layer structure. Show the method.

In FIG. 1, step (a) shows the step of forming the plasma polymerized film 1 on the thin film 2 to be processed having a large step. The plasma polymerized film 1 is a thin film having a property that a chemical reaction occurs when it is irradiated with ultraviolet rays, far ultraviolet rays, electron beams, X-rays, etc., and the solubility of a specific solvent changes, and pattern formation can be performed using this. Is.

In step (b), a desired pattern is baked (exposed) on the plasma polymerized film 1 and developed to form a resist pattern.

Next, in step (c), the resist pattern is transferred to the thin film 2 to be processed by etching, for example, by ion milling with Ar ions.

Next, a pattern forming method using a two-layer laminated film which is a more preferable embodiment of the present invention will be described with reference to FIG. In the step (d), the thin film 2 to be processed having a large step is easily etched by oxygen plasma, and
A process of forming a material that is hard to be physically sputtered, for example, the carbon film 3 will be shown. The carbon film is formed by the following means.

I) Plasma CVD method in which a gas containing hydrocarbon is decomposed in plasma to deposit a carbon film ii) Sputtering method in which a carbon film is knocked out by ions of plasma with a target of carbon and is deposited on an opposing substrate iii ) Ion beam deposition method of ionizing a hydrocarbon gas and accelerating it to collide with a substrate to deposit a carbon film iv) Graphite vapor deposition method Next, in step (e), the plasma polymerized film 1 is formed. Plasma polymerization is performed as described below, for example. A vacuum chamber equipped with two electrodes (usually parallel plates) is evacuated and a monomer gas is introduced into the chamber. Then, a high frequency is applied between the electrodes to cause a discharge, and a plasma of a monomer gas is generated. The polymer is deposited on the substrate placed on the ground electrode. In order to suppress cross-linking as much as possible, it is usually better to choose weak plasma conditions. For example, it is preferable that the applied power is small, the substrate temperature is low, the monomer gas flow rate is small, and the monomer gas pressure is set high.

Next, in step (f), a desired pattern is formed on the plasma polymerized film 1 by exposure and phenomenon.

In step (g), the carbon film 3 is etched by using the pattern of the plasma polymerized film 1 as a mask. The etching of the carbon film is preferably dry etching using oxygen plasma. More preferable is reactive ion etching (hereinafter abbreviated as RIE) using oxygen plasma. As described above, by using RIE having excellent anisotropy, the resist pattern can be accurately transferred to the lower layer material (carbon film 3).

Finally, in the step (h), the thin film 2 to be processed is patterned by using the pattern formed on the carbon film 3 as a mask. For this patterning, ion milling of Ar ions or ion beam etching is usually used. After the completion of this step, the remaining carbon film 4 may be left as it is and moved to the next step.
It can also be removed by etching with oxygen plasma (not shown). Next, specific examples will be described in detail.

Example 1 Permalloy was sputtered on a silicon wafer having a diameter of 3 inches having a stripe pattern of a line-and-space polyimide resin having a depth of 10 μm and a width of 50 μm (Hitachi Chemical Co., Ltd .: PIQ) to a thickness of 1 μm. Formed. Plasma-polymerized film of phenylfluorosilane on top of this is 1.6 μm
Was formed as described below.

That is, the radius is inside the stainless steel vacuum chamber.
A ground side electrode of a plasma CVD apparatus having a pair of 10 cm disk-shaped parallel plate electrodes, one of which is electrically connected to a high frequency power source through a matching box, and the other is grounded together with a vacuum chamber. The substrate was placed on the above and the substrate was water-cooled. Next, after evacuating the inside of the vacuum chamber to a degree of vacuum of 1 × 10 to ³ Pa or more, phenylfluorosilane was supplied at a rate of 15 ml / min, and the exhaust rate was adjusted to adjust the pressure in the vacuum chamber to 13.3 Pa. Kept on. Next, high-frequency power having a frequency of 13.56 MHz and a power of 50 W was applied to the high-frequency applying electrode to generate plasma, which was held for 80 minutes, the application of high-frequency power was stopped, and the substrate was taken out. A 1.6 μm thick phenylfluoropolysilane was formed.

A photomask having a line-and-space striped pattern with a width of 5 μm was arranged on the thin film thus formed so as to be orthogonal to the polyimide resin pattern, and ultraviolet light of 300 mJ / cm ² (365 nm) was obtained. Was irradiated, and it was immersed in methyl cellosolve to cause a phenomenon. As a result, a positive resist pattern was formed, and permalloy was exposed in a portion where there was no resist pattern.

Next, the exposed permalloy was etched by ion milling of Ar ions. The ion milling conditions were as shown below.

Acceleration voltage 700V Deceleration voltage 200V Arc voltage 80V Ar flow rate 15 ml / min Ion incident angle 0 ° The line width of the line-and-space pattern of the permalloy thus formed was measured, and the dimensions at 30 points on the substrate surface were measured. The variation was 4.85 ± 0.27 μm, which had excellent accuracy. Further, the pattern shape was also good and no reattachment was observed.

Comparative Example In exactly the same manner as in Example 1, a depth of 10 was formed on a silicon wafer.
A line-and-space polymide-based resin pattern having a width of 50 μm and a width of 50 μm was formed, and permalloy was further formed thereon to a thickness of 1 μm.

A plasma polymerized film of methyl isopropenoketone was formed on this substrate to a thickness of 2.0 μm. The film forming conditions are shown below.

Monomer flow rate 40 ml / min Monomer pressure 13.3 Pa RF power 80 W Substrate temperature 70 ° C. Using the same photomask as in Example 1 for the resist thus obtained, an attempt was made to form a pattern of 400 m.
With far-ultraviolet light having an exposure amount of J / cm ² (254 nm), no pattern appeared at all when the phenomenon occurred with ethyl alcohol. Therefore, further 8000 mJ / cm ² (254
(nm) It became a resist with a clear positive pattern only after additional exposure, and the sensitivity was lower than that of Example 1 by one digit or more.

Example 2 In the same manner as in Example 1, a line-and-space polyimide resin pattern having a depth of 10 μm and a width of 50 μm was formed on a silicon wafer having a diameter of 3 inches. A 1 μm permalloy was formed.

A carbon film having a thickness of 1 μm was formed on this substrate by the following procedure. That is, an electrode structure having a pair of disk-shaped parallel plate electrodes with a radius of 10 cm inside a stainless steel vacuum chamber, one of which is electrically connected to a high frequency power source through a matching box, and the other is grounded together with the vacuum chamber. The substrate was placed on the high frequency application side electrode of the plasma CVD apparatus having the above, and the substrate was heated to 200 ° C. 1 x 10 vacuum chamber
After evacuating to a vacuum degree of ~ ³ Pa, add 1-min of n-hexane per minute.
0 ml was supplied and the exhaust rate was adjusted to maintain the pressure at 2.6 Pa. Next, frequency 13.56MHz, power 200W
The high frequency power was applied to generate plasma, the discharge state was maintained for 20 minutes in this state, and then the high frequency power was stopped.

Then, on this substrate, in the same manner as in Example 1, phenylfluoropolysilane having a thickness of 0.4 μm was formed from phenylfluorosilane. The plasma polymerization conditions are as shown below.

Monomer flow rate 15 ml / min Monomer pressure 13.3 Pa RF power 50 W Polymerization time 20 min Substrate temperature 20 ° C. Then, the same photomask as in Example 1 was used for this thin film so as to be orthogonal to the lower polyimide resin pattern. After being arranged, it was irradiated with 250 mJ / cm ² (365 nm) of ultraviolet light and then developed to obtain a positive pattern.

Next, this substrate was placed on the same vacuum device and on the same electrode side as when the carbon film was formed, evacuated to 1 × 10 to ³ Pa, and oxygen gas was introduced at 10 ml / min. The pressure was set to 2.6 Pa, and high frequency power of 200 W was applied for 30 minutes. As a result, the permalloy in the portion without the resist was etched and exposed, and the resist pattern was transferred to the carbon film.

Next, ion milling of permalloy was performed as follows. The substrate is set on the substrate holder of the ion milling machine, and the acceleration voltage is 700V and the deceleration voltage is 200V.
Ion milling was performed for 20 minutes under the conditions of V, arc voltage of 80 V, Ar flow rate of 15 ml / min, and ion incident angle of 0 ° to remove the permalloy in the exposed portion.

The dimensional variation of the pattern formed as described above at 30 points on the substrate surface is 5.55 ± 0.40 μm.
And the processing accuracy was excellent. Further, redeposition was not observed on the side wall of the pattern.

Embodiment 3 Next, the processing of the magnetic film for controlling the track width of the thin film magnetic head will be described below with reference to FIGS. 3 and 4.

Permalloy was sputtered to a thickness of 1.5 μm on a non-magnetic substrate 4 having a diameter of 3 inches to form a lower core layer 5 by a photoetching technique.

Next, alumina is sputtered to 0.5
The gap layer 6 is formed with a thickness of μm and is formed by using a photo etching technique.

Subsequently, a polyimide resin (trade name: PIQ, manufactured by Hitachi Chemical) is spin-coated, then heat-cured and patterned by photoetching technique to form a first layer having a thickness of 2 μm.
Insulating film 7 of

Further, Cu is formed to a thickness of 1.5 μm by sputtering, and is patterned into a coil 8 in a spiral shape by using a photoetching technique to form the coil 8.

An insulating film of polymide resin was formed on the coil 8 to form a second insulating layer 9 having a thickness of 2.5 μm.

Subsequently, permalloy is sputtered to a thickness of 1.5 μm to form a uniform upper core layer 10.

The upper core layer 10 thus formed was patterned in the same manner as in Example 2. That is, the pattern of the upper core layer 10 was formed by using a two-layer film of a carbon film and a plasmic film of phenylfluorosilane. FIG. 4 shows a pattern of the carbon film 3 using the plasma-polymerized polysilane film 1. The width of the tip end portion of the upper core layer 10 in FIG. 3 becomes the track width 11, and the dimensional variation at 30 locations within the substrate of this track width 11 is 7.
It was 3 ± 0.52 μm, indicating high processing accuracy. Further, no redeposition was observed on the side surface of the pattern.

After the above steps, an alumina protective film is formed on this substrate, a terminal portion is formed, and the substrate is cut into sliders, and a thin film magnetic head is obtained through gap processing and rail processing. The writing and reading performances of the thin film magnetic head finally obtained in this manner were practically satisfactory. Moreover, there was no problem in reliability in long-term use.

[0065]

According to the present invention, high sensitivity of the plasma-polymerized film can be achieved by using the plasma-polymerized polysilane. Further, since the resist can be formed on the substrate having the step portion with a substantially uniform thickness, the dimensional accuracy after development can be improved. Further, since the thickness of the resist can be thinned even in the concave portion of the step, it is possible to prevent reattachment at the time of ion milling, and it is possible to improve the processing pattern accuracy and the sectional shape.

[Brief description of drawings]

FIG. 1 is a process chart showing an embodiment of the present invention.

FIG. 2 is a process drawing showing another embodiment of the present invention.

FIG. 3 is a plan view of a part of the thin film magnetic head of the present invention.

FIG. 4 is an enlarged cross-sectional view taken along the line X-X ′ of FIG.

[Explanation of symbols]

1 ... Plasma polymerized film, 2 ... Thin film to be processed, 3 ... Carbon film, 1
0 ... upper core layer, 11 ... track width

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Reference number within the agency FI Technical indication location H01L 21/027 21/302 H 7353-4M (72) Inventor Atsushi Atsushi Yoshida Totsuka-ku, Yokohama-shi, Kanagawa Prefecture 292, Machi Co., Ltd., Hitachi, Ltd., Production Technology Laboratory (72) Inventor, Tomoko Hiraiwa, 292, Yoshida-cho, Totsuka-ku, Yokohama, Kanagawa Prefecture, Ltd. (72), Hitachi, Ltd. Hitachi, Ltd. Odawara factory

Claims (4)

[Claims] 1. A resist pattern is formed on a substrate having a large height difference in a surface to be processed, and a dry etching method mainly consisting of physical sputtering method is used to remove a material to be processed in a portion without a resist to form a pattern. In the method, the resist is polysilane composed of a repeating unit represented by Chemical Formula 1 or Chemical Formula 2 formed by plasma polymerization, and the film thickness of the resist in the surface to be processed is made uniform. Forming method. [Chemical 1] However, R ₁ and R ₂ represent different groups selected from a fluoro group, a perfluoroalkyl group, a phenyl group, a perfluorophenyl group, and a perfluoroalkyl-substituted phenyl group. [Chemical 2] However, R ₃ represents a perfluoroalkyl group or a perfluoroalkyl-substituted phenyl group. 2. A second layer, which is hard to be removed by the oxygen plasma and which can be patterned by electromagnetic wave or particle beam irradiation and a phenomenon, is formed on the first layer removable by the oxygen plasma. In a method of patterning a material to be processed of a substrate having a large height difference in a surface to be processed by using a laminated film having a layer structure, the second layer is formed by plasma polymerization and is represented by chemical formula 3 or chemical formula 4. A pattern forming method comprising a repeating unit consisting of polysilane. [Chemical 3] However, R ₁ and R ₂ represent different groups selected from a fluoro group, a perfluoroalkyl group, a phenyl group, a perfluorophenyl group, and a perfluoroalkyl-substituted phenyl group. [Chemical 4] However, R ₃ represents a perfluoroalkyl group or a perfluoroalkyl-substituted phenyl group. 3. The pattern forming method according to claim 2, wherein the first layer is a carbon film. 4. A thin film magnetic head in which a magnetic material for controlling a track width of the thin film magnetic head is patterned by using the pattern forming method according to claim 1.